A usual method for in-flight refueling operations illustrated in FIG. 1 is based on the use of a boom 18 for interconnecting a tanker aircraft 13 with a receiver aircraft 11. The boom 18 is basically a telescopic or extensible tube attached to the underside of the tanker aircraft 13 by means of an articulation element that provides fuel passage from the tanker aircraft 13 to the receiver aircraft 11. At the tanker aircraft 13, the operator controls visually all steps and procedures for a safe refueling operation. In particular, the operator controls the boom movements until it makes a physical connection with the receptacle of the approaching receiver aircraft 11. Once the refueling operation is finished in a certain session, the boom 18 is hoisted up to its secured position in the tanker aircraft 13.
Another usual method for in-flight refueling operations is called probe and drogue. As illustrated in FIG. 2, this refueling system method employs a flexible hose 19 that trails from a pod 17 in the tanker aircraft 13. The drogue 21 is a fitting resembling a windsock or shuttlecock, attached at its narrow end with a valve to the flexible hose 19. The drogue 21 stabilizes the hose 19 in flight and provides a funnel to aid insertion of the receiver aircraft probe 25 into the hose 19. The hose 19 connects to a drum unit and, when not in use, the hose/drogue is reeled completely into the cited drum unit in the tanker aircraft 13. The receiver aircraft 11 has a probe 25, which is a rigid arm placed on the aircraft's nose or fuselage. This probe 25 is often retracted when not in use, particularly on high speed aircraft. At the end of the probe 25 is a valve that is closed until it mates with the drogue 21, after which it opens and allows fuel to pass from tanker aircraft 13 to receiver aircraft 11.
The refueling operations described above are very sensitive and must be effected in a very precise and accurate way because of security reasons. Particularly a so-called “broken probe” (actually a broken fuel valve, as described above) may happen if a poor flying technique is used by the receiver pilot, or in turbulence.
To facilitate in-flight refueling operations with the above-mentioned methods the prior art teaches the use of different signaling systems in the tanker aircraft and/or in the refueling device to help the pilot of the receiver aircraft in the approach operation to the tanker aircraft as complementary means to radio communications between the tanker and receiver aircraft.
Even though said signaling systems have improved the aerial refueling operations, radio communication between the tanker aircraft and the receiver aircraft are still needed. As this communication means cannot be used in a radio silence environment there is need of a communication system available in said environment.